1. Field of the Invention
The present invention relates to a method and an apparatus for mixing a powder with a liquid, and more specifically to a method and an apparatus for mixing a powder with a liquid by spraying the liquid to the powder loaded in a mixing container and rocking the container, a mix manufactured by the method, and a compact and a sintered body obtained from the mix.
2. Description of the Related Art
According to a conventional method of mixing of this kind, as disclosed in the Publication No. 5-38829 of Examined Japanese Utility Model Application for example, the powder is loaded into the container, and the container is rotated and rocked while the liquid is being sprayed from a nozzle disposed generally at a center portion of the container, thereby agitating the powder in the container for mixing with the liquid.
However, according to such a method as above, since the container is rotated and rocked while the liquid is being sprayed from the nozzle, there is much opportunity for the nozzle to be contacted by the powder. When the powder contacts the nozzle, the powder sticks to the nozzle, partially clogging a spraying port, making impossible to maintain uniformity in the spraying, leading to a problem of poor mixing. Another problem is that the powder stuck to the nozzle absorbs the liquid excessively, making localized doughy mass.
It is therefore a primary object of the present invention to provide a method and an apparatus for mixing the powder with the liquid capable of avoiding the non-uniform supply of the liquid caused by the powder covering the spraying port of the liquid, and preventing the liquid from dripping out of the spraying port.
Another object of the present invention is to provide a mix manufactured by the above method, and a compact and a sintered body obtained from the mix.
According to an aspect of the present invention, there is provided a method for mixing a powder with a liquid, comprising; a first step of supplying the liquid to the powder in a mixing container by a supplying portion exposed to an inside of the mixing container, and a second step of mixing the powder with the liquid by rocking the mixing container.
According to the present invention, the step of supplying the liquid toward a surface of the powder and the step of mixing the powder with the liquid are different steps separated from each other. Specifically, the powder is mixed with the liquid after a desired amount of the liquid is supplied. When the step of mixing the powder with the liquid starts, the supply of the liquid is already finished, and therefore, the powder does not stick to the supplying portion when the liquid is supplied, and the liquid can be supplied uniformly to the surface of the powder. Thus, the non-uniform supply of the liquid caused by the powder covering the supplying port of the liquid and dripping of the liquid from the supplying port can be avoided, thereby preventing the formation of the localized doughy mass, making possible to mix the powder with the liquid efficiently and uniformly.
According to the present invention, preferably, in the second step, the powder is mixed with the liquid after the supplying portion has been evacuated from the mixing container. With this arrangement, it becomes possible to prevent the powder from sticking to the supplying portion. Therefore, the supply portion is not worn by the powder, making possible to extend the life of the supplying portion.
Further, preferably, the mixing container is tilted at 10 degreesxcx9c40 degrees off the horizontal level while the liquid is supplied to the powder. In this case, the liquid can be supplied more uniformly to the surface of the powder. Therefore, when the powder is mixed with the liquid, the formation of the localized doughy mass caused by non-uniform supply of the liquid is prevented, making possible to mix the powder with the liquid more efficiently and uniformly.
Further, preferably, the mixing container is hollow cylindrical having a length 1.5xcx9c2.5 times an inner diameter, and loaded with the powder to 30%xcx9c80% of the capacity of the mixing container. By supplying the liquid toward the surface of the powder under this condition, the liquid can be supplied more uniformly to the surface of the powder. Therefore, when the powder is mixed with the liquid, the formation of the localized doughy mass caused by non-uniform supply of the liquid is prevented, making possible to mix the powder with the liquid furthermore efficiently and uniformly.
Preferably, the mixing container includes an opening, and the method further comprises a third step after the second step, of unloading a mix from within the mixing container while giving the mixing container rotation and impact as well as tilting the mixing container to position the opening at a downward location. With this arrangement, the mix in the mixing container can be unloaded efficiently, reducing a residue remaining in the mixing container, guaranteeing the uniform mixing in the mixing operation in the next cycle.
Further, preferably, the mixing container is rotated while the liquid is supplied. In this case, the liquid can be supplied uniformly to the surface of the powder. This is especially effective when a large amount of the liquid is supplied, since the liquid can be supplied to the whole mass of the powder. Further, by rotating but not rocking the mixing container, the powder can be prevented from sticking to the supplying portion.
Further, preferably, the powder includes a metallurgical powder, and the liquid includes at least either one of a lubricant and a binder. In this case, if the method for mixing a powder with a liquid described as above is applied, a uniform mixing can be achieved, making possible to prevent failures such as breakage after sintering.
Preferably, the metallurgical powder includes a rare-earth alloy. The rare-earth alloy is highly abrasive, being apt to wear the mixing container. However, according to the above method for mixing a powder with a liquid, it becomes possible to mix uniformly within a short time. Therefore, even when the rare-earth alloy is mixed, it becomes possible to reduce the wear in the mixing container to a very low level.
According to another aspect of the present invention, there is provided a mix of a powder and a liquid obtained by; first supplying the liquid to the powder in a mixing container from a supplying portion exposed to an inside of the mixing container, and then mixing the powder with the liquid by rocking the mixing container. If a mix is manufactured in such a method as above, the mix is uniformly mixed.
According to still another aspect of the present invention, there is provided a compact manufactured from a mix obtained by; first supplying a liquid to a powder in a mixing container from a supplying portion exposed to an inside of the mixing container, and then mixing the powder with the liquid by rocking the mixing container. If such a mix as above is used, it becomes possible to reduce breakage and cracking of the compact at a time of pressing, making possible to improve yield of the compact.
According to still another aspect of the present invention, there is provided a sintered body manufactured from a mix obtained by; first supplying a liquid to a powder in a mixing container from a supplying portion exposed to an inside of the mixing container, and then mixing the powder with the liquid by rocking the mixing container. If such a mix as above is used, it becomes possible to reduce breakage and cracking of the compact at a time of sintering the compact, making possible to improve yield of the sintered body.
According to still another aspect of the present invention, there is provided an apparatus for mixing a powder with a liquid, comprising; a mixing container for holding the powder, a supplying portion exposed to an inside of the mixing container when the liquid is supplied to the mixing container while being evacuated from the mixing container when the powder is mixed with the liquid within the mixing container, and a rocking portion for rocking the mixing container for mixing the powder and the liquid. If this mixing apparatus is used, the powder can be mixed uniformly with the liquid.
According to the present invention, preferably, the supplying portion is constituted to prevent the liquid from discharging when the supply of the liquid is not needed. Since the supplying portion can prevent the discharge of the liquid when the supply of the liquid is not needed, it becomes possible to prevent dripping of the liquid from the end portion of the supplying portion after a desired amount of the liquid has been supplied. Therefore, the formation of the localized doughy mass caused by the dripping liquid can be prevented, and the powder can be mixed with the liquid efficiently and uniformly.
Further, preferably, the supplying portion includes a cylindrical spray tube having an end portion provided with a supplying port, a stop rod axially slidable within the spray tube, an urging portion urging the stop rod in a direction for closing the supplying port, and a first pressurizing portion opening the supplying port by application of a pressure in the opposite direction of the urge. In this case, since the urging portion always urges the stop rod in the direction for closing the supplying port, and the port is opened by the pressure in the opposite direction of the urge when the liquid is supplied, it becomes possible to prevent the liquid remaining in the spray tube from dripping out of the supplying port when the supply is stopped.
Further, preferably, the apparatus further comprises a second pressurizing portion applying a back pressure to the liquid for supply of the liquid to the supplying portion. As described above, since the supply of the liquid to the supply portion is performed by addition of the back pressure, and the stopping of the supply is made by closing the supplying port, it becomes possible to keep a constant pressurization to the liquid, making possible to prevent pulsing in the liquid. Therefore, since a constant state of supply can be maintained, the liquid can be sprayed uniformly.
The object described above, other objects, features, aspects and advantages of the present invention will become clearer from description of an embodiment to be made hereinafter with reference to the attached drawings.